This invention relates to benzobisthiazole polymers with thiophene moieties.
In recent years, there has been considerable interest in organic pi-electron conjugated polymers as nonlinear optical (NLO) materials. In addition to potentially high third-order NLO properties with very short response times, these organic polymers offer the flexibility for molecular modification leading to the requisite processibility into various NLO-application forms with high mechanical, thermal and environmental stabilities. Theoretical calculations and experimental measurements indicate that the length and electron density of the pi-electron conjugation contribute substantially to the third-order NLO optical susceptibility, chi.sup.(3), of aromatic heterocyclic polymers.
High molecular weight rigid-rod poly(p-phenylenebenzobisthiazole) (PBT) can be obtained through the polycondensation of a diaminobenzenedithiol, e.g., 2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT), with terephthalic acid or terephthaloyl chloride in polyphosphoric acid (PPA). The PBT can be processed from PPA into fibers and films with outstanding mechanical properties and thermooxidative stability. Because of the highly delocalized pi-electron system along its backbone, PBT has been investigated as a promising third-order NLO material. PBT film extruded from PPA exhibits an unusually high chi.sup.(3) of 10.sup.-11 esu and a very short response time (.apprxeq.500 femtoseconds). In contrast, GaAs, generally considered to be one of the best inorganic NLO materials, has a response time of about 1 picosecond.
Accordingly, it is an object of this invention to provide novel benzobisthiazole polymers.
Other objects and advantages of the invention will be apparent to those skilled in the art.